CHAPTER 3 ME1HODOLOOY
3.1 Research Methodology and Project Activities
3.1.2 Chamber Design
In the mean time, the base of the chamber will be modify. Prior task include Autocad drawing and Mazak fabrication will be reproduced. The following is the picture of current of the chamber.
Figure 23 Original Chamber Base
The draft of the new chamber base would mainly based on HSE reason and effectiveness of the heat conservation. As shown in Fig 14.
Figure 24 Proposed New Chamber base
The heater is elevated by four insulator (e). The heater sit at the designed
aluminium plate (b). This may reduce the necessary heat to rise the chamber temperature. The temperature respond would be faster and effective. The gas outlet is place beneath the heater, (C), which allow the gas efficiently bath the test subject and reduce the risk of gas leakage. A hole is made for cable (d).
Proposing 4th: chamber modification. The four elevated insulator Fig. l4(e) will use the ceramic fiber as the proposed insulation material. It is a cheap and common insulator used widely in industrial section. The reason of using ceramic fiber is because it is Low thermal conductivity, low heat storage, stability at high temperatures, excellent resistance to thermal shock, chemical attack, water and oil damage, reduced refractory heat-up and cool-down time, light weight for ease of handling, cutting, drilling, sawing and machining, excellent acoustic insulation. [IS]
Properties and characteristics: Continuous use limit: up to 2300°F; melting point:
3200°F; thermal conductivity: 1.53°F per BTU-inlhr/ft2 at 1800° F ; density: 16 PCF (pounds per cubic foot); color: white [IS]
Utilizing a wet forming manufacturing process, the material combine a blend of alumina-silica ceramic fibers with both organic and inorganic binders to improve handling strength and ensure material integrity at high service temperatures. The ceramic fiber available in various form and shape that may fit the usage of the elevated stand. For, example, YESO 1260 may provide an appropriate solution for the chamber. The following is the samples of the ceramic fiber.
Figure 25 YESO ceramic fiber products
The following implementation as shown:
Figure 26 Ceramic fiber implementation
Further chamber modifications include chamber base alignment. The chamber base is not thick enough to create four screw sockets to support the heater.
Implementation in Fig. 20 will puncture the chamber base. Since the author is going to use MAZAK CNC machine to mill a new base, the advantage of this 5 axis milling machine could be taken to create some islands on the chamber base, replacing the screw design. The islands created act like the screw leg to elevate the heater from overheating the base. The finalized design of base is shown below
Figure 27 3D view of the finalize design of chamber base
Figure 28 Autocad Drawing of the new chamber base
This design provide a better cooling system for the chamber. It can hold the heater firmly and elevate the heater from the base at the same time. It is also designed with extra room to allocate the ceramic fiber. With the brittle characteristic of ceramic fiber, the small cylinder will crush when creating the screw railing in the ceramic fiber in Fig.20. In the new design, a block of ceramic fiber just place under the heater and some ceramic fiber placed at the side of the heater as shown. Those ceramic fiber
"padding" provide a better solution for heat insulation
heater
island
Ceramic
,----+---
fiberFigure 29 Insulator implementation from the top view
The 5th proposal is the 4 point probe. The probes are to measure the voltage across the thin film and the current through it. The possible material used will be the gold as it is stable in high temperature and excellent electricity conductor. In order to protect the thin film, adequate pressure shall be applied to the thin film so that it would be puncture and the contact is firm enough to conduct electricity. Therefore, a ball point tip is a suitable material.
The design of the probe is adaptable to all size of thin film. Therefore, a aluminum probe holder with adjustable plane movement will be install on top of each island. The concept illusion of a probe as shown:
Gold
Aluminum Probe holder
Thin ilm
Figure 30 One of the 4 point probe
Due to no ceramic fiber solid found, the ceramic fiber solid will be replaced with the ceramic fiber fabric insulator. The fabric insulator has the similar property with the ceramic fiber solid, it has high temperature resistant up to 1 OSOA °C. Ceramic fiber textiles also feature excellent properties of lightweight, low thermal conductivity and chemical stability resisting attack from most corrosive agents. It has widely used as good materials for electrical insulation, thermal plastic reinforcement and heat insulation, due to their out standing physical properties, such as high tensile strength, low moisture absorption, good heat-resistance and chemical resistance, and diamentional stability.
Figure 31 Ceramic Fiber Textile
The chamber base will be fabricated in Mazak V ariaxis 630 milling machine.
MILLIHD
M.AZA& V.._.IAllliS 630
Figure 32 Mazak V ariaxis 630 milling machine
However, the design of the chamber base is not feasible to the machine due to the end mill restriction. The small end-mill 3.5mm diameter is incapable to reach the depth of 15mm as the vibration would be very significant at such a depth. Therefore, the larger end-mill has to be use. By selecting the larger end-mill of 4mm, it would have collision path with the side islands since the island and the diameter wall is only 3.75mm.
Figure 33 Side island 3.75mm restriction
To adapt the restriction, The chamber base has to be design again. However, the change of ceramic fiber solid to ceramic fiber textile provide an excellent advantage to ease the design, as the thickness of the textile is only 1.3mm.
Y -
Figure 34 Chamber base that fits the Ceramic fiber textile and solve the machining restriction
The chamber base will be design based on the characteristic of the of the ceramic fiber textile. The 4 pole supporting system no longer can support the textile form of ceramic fiber. A flat plate will created to place the ceramic fiber with air duct beneath it. To still the ceramic fiber textile position in the chamber, red silicon gasket maker will be used. A fully cured silicon gasket can withstand the temperature up to 343 degree Celsius. It is a paste like, one component material which cures to a tough, rubbery solid upon exposure to moisture in the air. It is sensor safe and manufactured to meet the OEM specification. It can resists cracking and migration cause by thermal cycling; will not lead; resist water, oil and anti-freeze.
Figure 35 Complete Chamber Base
To ensure the gas quality in the chamber, the leakage or air contamination inside the chamber has to be minimal. Therefore, 6 L-shape cavity duct is made to carry the 4 point probe signal cable and the power supply for the heater.
islands Chamber
duct
Figure 36 Cross Section view of the chamber base with wire duct
The author loss 2 L-shape duct due to some drilling accident when the drill bit is broken inside the chamber base. One manage to recover by using superdrill to remove the broken bit debris inside the chamber. Another is aborted due to the drill bit broken was too deep to remove. Therefore, the current efficient wireduct is 5 L-shape wireduct.
Figure 3 7 Implementation of the heater thru the L-shape duct
3.1.3 MisceUaneous Issues and Accessories
The project freatured LCD , a commonly used 2-line x 20 characters display.
This module can operate in 2 modes, an 8-bit interface and 4 bit interface using high order data lines. An 8-bit data interface requires less programming, but uses more I/0 pins. A 4-bit data interface uses only 7 1/0 pins, but requires more programming.
The project also featured a matrix key-pad, the key is connected in rows and columns. When a key is pressed, the corresponding row and column make contacts
and provide logic 0, and the software recognizes the key pressed and encodes the key.
The following illustration includes an interfacing of 4x4 keypad to PORT B.
e~o~e l
Figure 38 Keypad layout
To recognize and encode the key pressed, the concept is to ground all the columns by sending zeros and check each key in a row for logic 0. The key that is pressed will read as logic 0. This can be accomplished by setting the column section ofPORTB as output and the row section as input. The program will check for a key closure by reading the input port and debouches the key. If a key is closed, the input reading will be less than all 1 s. When a key is closed, the input reading for four keys is the same. For example, when any of the key of 1st row is pressed, the input reading on the lines RB4-RB7 is the same: 0111. To identify the key, the program grounds one column at a time and checks all the rows in that column. Once a key is identify, it is encoded based on its position in the column.
3.1.4 S~~~~~ple PreJNUIIIion
In order to use the van der Pauw method, the sample thickness must be much less than the width and length of the sample. In order to reduce errors in the calculations, it is preferable that the sample is symmetrical. There must also be no isolated holes within the sample. The measurements require that four ohmic contacts be placed on the sample. Certain conditions for their placement need to be met:
a) They must be on the boundary of the sample (or as close to it as possible).
b) They must be infinitely small. Practically, they must be as small as possible; any errors given by their non-zero size will be of the order D I L, where D is the average diameter of the contact and L is the distance between the contacts.
Squal"l'or Square or rwta~le:
Clonrl~f redan:k: tontacts at ~ rdgH contads at or insillr th~
4 tM t'omr:rs prrimrtrr
B OD
2 3
(a) (b) (c)
Preferred Acceptable Not Recommrnded
Figure 39 Thin film resistivity measurement orientation
In addition to this, any leads from the contacts should be constructed from the same batch of wire to minimise thermoelectric effects. For the same reason, all four contacts should be of the same material.r211
1 .---, 4 Thin Film
2 3
Figure 40 Edge of thin film to sample voltage and pump in current
a) The current J12 is a positive DC current injected into contact 1 and taken out of contact 2, and is measured in amperes (A).
b) The voltage V34 is a DC voltage measured between contacts 3 and 4 with no externally applied magnetic field, measured in volts (V).
c) The sheet resistance Rs is measured in ohms (0).
To make a measurement, a current is caused to flow along one edge of the sample (for instance, In) and the voltage across the opposite edge (in this case, V34) is
measured. From these two values, a resistance (for this example, R12,34) can be found using Ohm's law:
(3-1)
In his paper, van der Pauw discovered that the sheet resistance of samples with arbitrary shape can be determined from two of these resistances - one measured along a vertical edge, such as R 12,34, and a corresponding one measured along a horizontal edge, such as R23,4l· The actual sheet resistance is related to these resistances by the van der Pauw formula
(3-2)
We define
(3-3)
And
R23 •• + R4t 23
R horrzontal = '
2 ' (3-4)
Then, the van der Pauw formula becomes
(3-5)
In general, the van der Pauw formula cannot be rearranged to give the sheet resistance Rs in terms of known functions. The most notable exception to this is when
Rverticot = R = Rhorizontat; in this scenario the sheet resistance is given by
R = -trR
s ln2 (3-6)
3.2 Key milestone and Gantt Chart Please refer to Appendix
3.3 Tools & Hardwara
3.3.1 H1Jrdw1Jres
Ceramic heater
Aluminum/steel chamber
MAZAK 5 axis milling machine Multimeter
DC power supply RTD sensor
3.3.2 SojtwiJres
PSIPCE MATLAB MULTISIM
PIC simulator and Programmer Visual Basic
AutoCAD MPLab
PIC Simulator IDE
Figure 41 PIC Simulator
CHAPTER4
RESULT AND DISCUSSION
4.1 P controller simulation
Below is the simulation done by the proportional controller. The simulation is based on the 2nd order system. Assume the desire output is 2.
The simulation is to check the effect of the controller gain Kp to the steady state error.
WhenKp=5,
Figure 42 2"d order Kp=5 [5]
Output= 1.87807
WhenKp=lO
Figure 43 2"d order Kp=10 [5]
Output= 1.90475
WhenKp= 15
Figure 44 2"d order Kp=l5 [5]
Output= 1.93540
From the simulation, the higher the gain, the smaller the steady state error, but the larger the percent overshoot. Note that the output is closer to 2 as the proportional gain Kp increase. However, the error is still exist until the end of the simulation because there is no integral action to compensate the error.
4.2 Temperature Control Result
Figure 45 Step respond from 270 degree to 290 degree
Tuning Parameter PB=lOO%, Ti=12s, Td=3s
Settling Time (Fluctuation set between 2 degree C)= 48 minutes Rise Time = 6 minutes
Close Lid temperature fluctuation= +/-0.3oC Open Lid temperature fluctuation= +/-1.6oC
I I I • • I I
I I t1f/11 I I
..
I I I I I I I I I I
..
Figure 46 Temperature output respond (Read graph from right to left)
Red: MY (power supplied to heater) Blue: set value
Green: Current temperature
The recording rate is 250mmlhr. From the output respond, the graph shows a underdamp respond with quarter amplitude damping. This kind of respond is fast, zero offset and stable, with minimal rise time and settling time. The tuning method used is Ziegler Nichols tuning and some fine tuning. Below shows the tuning parameter.
RuJeName Tuning Parameters
Classic Nichols
Ziegler- Kp = 0.6 Ku Ti = 0.5 Tu Td =
0.125 Tu
Pessen Integral Rule
Some Overshoot
No Overshoot
Kp = 0.7 Ku Ti = 0.4 Tu Td
=
0.15 Tu
Kp
=
0.33 Ku Ti=
0.5 Tu Td=
0.33 Tu
Kp = 0.2 Ku Ti = 0.5 Tu Td = 0.33 Tu
The temperature control also respond well to disturbance also. Notice that the sudden drop of current temperature (green color) will cause the controller to increase the MV(red color), the power to the heater.
• • • 8 I I I I I~ I 1.1 I I I I I I I
Figure 4 7 Disturbance respond
I
\
r· l-- '
I . \
\ _/' \ ;
-·
'4.3 Fabricated Chamber Base and Gold Probe
Figure 48 Chamber Base
The chamber base fabricated in MAZAK is very precise and all dimension fit accurately. The chamber will soon implement with the probes and wiring duct.
'
Figure 49 4 point probe made from goldFabrication of 4 point probe is successful and ready to implement into the chamber.
CHAPTERS CONCLUSION
To cope with the temperature fluctuation, the PID controller can be considered. The proportional action will reduce most of the fluctuation which normally generated by the on-off controller. This is because the proportional controller can vary the intensity of heat needed in order to bring the temperature to steady state while the on-off controller can only have two distinct state. Integral action will eliminates the steady state error and the derivative action will reduce the settling time. The proposed chamber would be more efficient, sensitive and save with the elevation of the heater. The respond with the desire temperature input wonld faster too.
REFERENCES
[1] Retrieved 7/9/2008, http://www.rkcinst.co.jp/english/control_ Ol.htm,
[2] Retrieved 7/9/2008, http://en. wikipedia.org/wiki/Control_ system,
[3] Ong Yin Chee, Mohamad Shukri b. Zainal Abidin, June 2006, "Design and Development of Two wheeled Autonomous Balancing Robot", http://ieeexplore.ieee.org/iel5/4339287/4339288/04339332
[4] Retrieved 7/9/2008,
http://www.omega.com/prodinfo/temperaturecontrollers.html
[ 5] Retrieved 1119/2008,
http://www.facstaff.bucknell.edu/mastascu/eControlHTML/lntrollntro2.html
[6] NormanS. Nise, "Control System Engineering", 4th Ed. John Wiley & Sons.
Inc., 2004
[7] Emine Dogru Bolat, Kadir Erkan and Seda Postalcroglu, November 2005,
"Experimental Autotuning PID Control ofTemperature Using Microcontrller",
http://ieeexplore.ieee.org/iel5/1 0849/34189/01629912. pdf?tp=&isnumber=&a mumber= 1629912
[8] S.M. Radaideh and M. T. Hayajneh, "A modified PID controller (Plla~D)", Volume 339, Issues 6-7, September-November 2002, Pages 543-553
[9] Santina/Stubberud/Hostetter, "Digital Control System Design", 2"d Ed
[1 0] Retrieved 1119/2008, http://www.ecircuitcentllr.com/Circuits/pid11pidl.htm
[11] Retrieved 1119/2008, http://www.lakeshore.com/temp/cn/331m.html
[12] Retrieved 1119/2008,
http://www.facstaff.bucknell.edu/mastascu/eControlHTML/Introllntro3.html
[13] Karl J.
Asttoma,
Pedt1i Albertosb and Joseba Quevedo, "PID control", Volume 9, Issue 11, November2001, Pages 1159-1161[14] Kortvelyessy, Laszlo, 05/17/1977, "High tlmlperature heat insulation", http://www.freepatentsoniine.com/4024338.html
[15] Retrieved 13/10/2008,
http:/ /www.agismfg.com/html/other _prod.html?gclid=COaSr70hop YCFQE _ egod6UvS6A
[16] Retrieved 13/10/2008, http://www.alibaba.com/product-
gs/20 1542990/1260 _ YESO _Ceramic _Fiber_ board_ Insulating.html
[17] ITO, Kikukatsu,Iwate University (3-18-8, Ueda, Morioka-shi, Iwate 0208550, JP)
ITO, Takanori,Iwate University (3-18-8, Ueda, Morioka-shi, Iwate 0208550, JP)
OSADA, Hiroshi,Iwate University (3-18-8, Ueda, Morioka-shi, Iwate
0208550, JP)
CHIBA, Shigeki,Iwate University (3-18-8, Ueda, Morioka-shi, Iwate 0208550, JP), ll/07/2007 , "Temperature Control Method And Temperature Controller", http://www.freepatentsonline.com/EP1852765.html
[18] Serhat YILMAZ, Burak TOMBALOGLU, Kursat KARABULUTLU, Yener GUMUS, Hasan DiNCER, "Temperature Control Applications By Means Of A PIC 16F877 Microcontroller'', University of Kocae1i, Electronics and Communications
www.emo.org.tr/resimler/ekler/bflJ9bb5df6533b6 _ ek.pdf
Research,
[19] Jivan S. Parab, Santosh A. Shinde, Vinod G, "Practical Aspects of Embedded System Design Using Microcontrollers"
[20] Ramesh S. Gaonkar, "Fundamentals of Microcontrollers and Applications in Embedded System", Thomson Delmar Learning
[21] Retrieved 4/5/2009, http:/ /en.wikipedia.org/wiki!V an_ der _ Pauw _method
APPENDICES
APPENDIX A
ON/OFF CONTROLLER SOURCE CODE
II Temperature controller based on PID //Source ofref.[l9]
#include<I6F877.h>
#use delay(clock=20000000) unsigned char a,i,bj;
void INITicd(void) ; void ENABLE (void) ; void LINE(int);
int keyb(void);
void dis(int);
int setpt= 60;
int kp= 12, ki=l,kd=ll,C=I;
void main( void) {
char test O=''PID";
char*p;
int j .new terror I. error2,rate= l.sum.currenttemp I;
setup_ adc __ports(ALL _ANALOG);
setup _adc(ADC _CLOCK _INTERNAL);
set_adc_channel(O);
INITlcdQ;
LINE(!);
P=&test;
for(j=O;j<l7;j++);
{
if{i==O)LINE(I);
if(j=8)LINE(2);
output_ d(*p++ );
ENABLEO;
delay_ms(IO);
While(!) { j=O;
j=keybO;
error I =setpt-currenttemptl;
newt=currenttemp I =kp*errorl;
sum=sum=error I;
newt=(newt--(kd*sum));
error2=error I;
if(newt>255;
sum=sum-error I;
}
If(newt<O) {
Newt=O;
Sum=sum-error I;
}
ourput_b(newt); //port B is connected to DAC0808 if((j=O)&&(C<I))
dis(Ox09);
delay-ms(IO);
if(C>=I)
} }}}
void ENABLE( void) {
output_ high(PIN _ E2);
delay_ms(IO);
output_low(PIN _ E2);
delay_ms(IO);
}
void LINE(int j){
if(j=l){
output _low(PIN-EO);output_low(PIN _ E I);
output_d(Ox80);
ENABLE();
output_ high(PIN _EO);
} else {
output_low(PIN_ EO);output_low(PIN_ El );
output_d()xCO); //PORT D LCD data lines ENABLE();
}}
void INITied(void) { output_low(PIN-EOO;//RS output_low(PIN_El);//RW output_Iow(PIN _ E2);//EL output_d(Ox38);
ENABLE();
ENABLE();
ENABLE();
ENABLE();
output_ d(Ox06);
ENABLE();
output_ d(OxOE);
ENABLE();
output_d(OxOI);
ENABLE();
}
iot keyb( void){
iotkey=O;
output_ c(OxFE) delay_ms(IO);
readkey=input_ c();
if{readkey=OxEE)key= I;
if{readkey==OxDE)key=2;
if{readkey=OxBE)key=3;
if{readkey=Ox7E)key=4;
return(key );
}
void dis(iot j) {
char code currenttemp[]~ "Tern~";
char code ioS(]~"decrement setpt";
char code dec[]~"decrement setpt";
char code ikp[]~"iocrement kp" ; char code dkp{l~"decrement kp" ; char code iki[]~"iocrement ki" ; char code dki[]=''decrement ki" ; char code ikd(]=''iocrement kd" ; char code dkd[]=''decrement kd" ; char *p;
if(j !=9){
INITicd();
if(j= 1 )p=&inS;
if(j=2)p=&dec;
if(j-3)p=&ikp;
if(j-=4)p=&dkp;
if(j=5)p=&iki;
if(j=6)p=&dki;
if(j=7)p=&ikd;
if(j=8)p=&dkd;
for(k=O;k> 17;k++
{
il\k==O)line(l);
if\k=8)line(2);
output_ d(*p++ );
ENABLE();
}
delay_ms(50);
lNITicd();
LINE(!);
output_d((setpt/100)+0x30));
ENABLE();
output_ d(((( setpt/1 0)% 1 O)+Ox30));
ENABLE();
output_ d( ((setpt% 1 O)+Ox30));
ENABLE();
delay-ms(500);
INITicd();
LINE(!);
output_ d((((kp/1 O))+Ox30)) ENABLE();
output_d(((kp%10)+0x30));
ENABLE();
delay_ms(50);
lNITicd();
LJNE(2);
output_d((((ki/IO))+Ox30)));
ENABLE();
output_d(((ki%10)+0x30));
ENABLE();